This invention relates generally to fuel injection systems, and more particularly to a method and apparatus for separating air out of fuel upstream from the fuel injectors.
Many fuel injection systems can have performance undermined by the presence of air mixed into the fuel. This can be especially true in systems, such as pump and line systems, that operate at lower injection pressures. At lower injection pressures, the air can remain in a bubble form and occupy volume that should otherwise be occupied by fuel. At higher injection pressures, such as injection pressures achieved in pressure intensified systems, mixed air is often forced into solution, and therefore has less effect on injecting a desired volume of fuel. Nevertheless, mixing of air in unknown quantities into a fuel supply can be undesirable in higher pressure systems because it can cause a combustion characteristics to deviate from expected combustion characteristics, potentially undermining the control of the same.
Pump and line fuel injection systems require low levels of air in the fuel supply, steady pressure regulation and short priming times. Injection timing retardation and/or engine power loss can be an indication that the fuel reaching the fuel injectors is over aerated. In other words, air in the fuel supply can cause delayed fuel injection opening pressures, resulting in fuel injection occurring later than expected in the injection cycle and less than the desired amount of fuel being injected. Steady pressure regulation is desirable so that the high pressure fuel injection pump performs in a predictable manner. Finally, excess cranking times that occur when starting a cold engine can be an indicator that the fuel circulation plumbing is experiencing excessively long priming times.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention, a fuel system for an engine includes fuel circulation plumbing with a fuel conditioning module. The fuel conditioning module includes an inlet passage, an inlet cavity, an outlet passage, a vent passage and an outlet cavity. The inlet cavity is separated from the outlet cavity by a baffle. The inlet passage opens to the inlet cavity and the outlet passage opens to the outlet cavity at locations elevationally below the top of the baffle. The vent passage opens to the outlet cavity at a location elevationally above the top of the baffle.
In another aspect of the present invention, a fuel conditioning module includes a housing having disposed therein an inlet passage, an inlet cavity, and outlet passage, an outlet cavity and a vent passage. The inlet cavity is separated from the outlet cavity by a baffle. The inlet passage opens to the inlet cavity and the outlet passage opens to the outlet cavity at locations elevationally below the top of the baffle. The vent passage opens to the outlet cavity at a location elevationally above the top of the baffle.
In yet another aspect of the present invention, a method of conditioning fuel includes dividing a mixture of fuel and air into a first portion having relatively large amounts of air and a second portion having relatively low amounts of air at least in part by separating an inlet cavity from an outlet cavity by a baffle. Routing the first portion into a vent passage that opens to the outlet cavity. Routing the second portion into an outlet passage that opens to the outlet cavity.